It has become customary to house electronic equipment, such as telecommunications equipment, in electronics chassis. Frequently, such chassis are designed to be rack-mountable to provide efficient storage for large quantities of equipment. In places where such large quantities of equipment are operated, space is typically at a premium. Accordingly, customers of chassis and racks are sensitive about devoting space to other than the equipment itself.
One type of chassis commonly encountered in rack-mountable form provides a means by which electrically to interconnect and cool equipment divided into modules and located in bays within the chassis. Such chassis are characterized by a rear cabinet and a hinged door on a front side thereof that can be opened to gain access to the modular equipment housed therein and closed to protect the modular equipment or to improve the cooling or appearance thereof.
It is necessary to provide a hinge for such doors that meets several, sometimes conflicting, requirements. First, the hinge should not add to the overall height of the chassis so as not to increase the overall height of the rack. Second, the hinge should not compromise the safety or structural integrity of the chassis as a whole; it should be able to withstand years of use. Third, the hinge structure should not impede the use of conventional equipment modules. In other words, the hinge should not protrude into the bays so as to interfere with the insertion or removal of equipment modules. Fourth, the hinge must not allow substantial EMI to escape from the chassis. Given the higher operating frequencies of today's telecommunications equipment, it is necessary to insure that long gaps that would allow radiation to escape from the chassis are not allowed to exist therein. Fifth, the hinge should not unduly add to the cost (material or labor) of manufacturing the chassis. Sixth, the hinge structure should not interfere with the serviceability of the chassis itself, apart from the equipment modules that may be located therein. Seventh, the hinge structure should not detract from the appearance of the front of the chassis. Eighth, the hinge structure should discourage significant amounts of air from passing into or out of the chassis around the door. As stated above, such chassis are frequently provided with a central cooling, requiring a defined flow for cooling air to be established through the chassis. Were the hinge structure to interfere with this flow by introducing an undesired inlet or outlet, the overall cooling capacity of the chassis could be compromised.
Finally, it is most desirable that the door be joined to the cabinet as a last step during manufacture thereof. The door usually is the most visible portion of the chassis and accordingly frequently contains graphics and other attractive designs that, were the door subjected to a larger part of the manufacturing process, could be damaged.
The obvious solution, and commensurate with that found in the prior art, is to provide a piano hinge that runs the length of the door. However, some chassis designs provide slots in the door to allow the equipment modules within the chassis to be viewed or contacted from without the chassis when the door is closed. The presence of the slots requires a piano hinge to be separated into many short lengths.
Some equipment modules require latches to engage and extract the modules from the backplane. To conserve space efficiencies, the latches are located low on the modules. Discontinuities must be introduced into a piano hinge to allow the latches to pass the hinge when the equipment modules are inserted into or removed from the chassis. Whether viewability or latch clearance is the issue in a given application, fabricating a discontinuous hinge to accommodate either can be quite difficult and expensive.
A less expensive solution is to eliminate the short lengths of piano hinge except for those at the extreme ends of the door. While this reduces somewhat the cost of manufacturing the chassis, the short lengths of piano hinge necessarily have long gaps therebetween that can admit or release EMI, degrading the electromagnetic performance of the chassis as a whole.
Therefore, what is needed in the art is a lower cost, more effective way of hinging a door to a cabinet to form an electronic chassis.